endean0

Can anyone help with a project that I am trying to put together.

I work from Home and am a House Husband. We have three kids of varying ages. My office is situated on the side of the house. I regularly work during the night and the Wife works shifts, so occaisionaly I am left to keep an eye on the kids at night. I find this a problem when they are asleep, as I have to keep break off to check that they are ok.

I need to build some sort of listening device with a range of about 20-30 metres. I've tried using high street devices but they are not brilliant. I also need to switch from room to room when monitoring.

The device itself needs to be as small as possible. My two year old regularly spots the Baby listener in her room and shouts down it or worst still unplugs it. I would like it to be battery opperated, longest life for smallest battery is key here.

So what I need are three small listening devices. A transmitter and a receiver that will allow me to switch between either of the three devices.

My emediate question is, will I be transgressing any laws in the UK by opperating such a device and will it cause any interferance to any channels or vital services?

Unfortunately I haven't got a load to spend on this, so as cost effective as possible would be of help.

Hope someone out there can give me some ideas.

Thanks

Nigel Goodwin

There are basically three available methods:

1) Wired intercoms.

2) Radio intercoms.

3) Mains connected intercoms.

1 - Wired intercoms would be the cheapest, but you would have to run the wires for them - however there are no legal restrictions.

2 - Radio intercoms, or baby alarms, these are usually single channel (particularly baby alarms). Radio transmissions are also strictly enforced in the UK - you either need a licence (very expensive, and very hard to obtain - if at all possible?), or to use licence free bands - but in this case you must use either ready built units, or at a minimum ready built radio modules, to comply with the licence free conditions.

3 - Mains wired intercoms work via low frequency radio signals transferred down the mains wiring, so generally only work on sockets on the same phase (usually all of them in a single house). These are available as multi-channel, and don't have any legal problems.

If you're going to run wires you could simply fit small microphones and pre-amplifiers in the rooms, running them all back to a common amplifier through a simple switch. This would be cheap, only have very small microphones in the rooms - but would require running cables.

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stevez

Your explanation suggests that you already have a 'baby listener' and I'd have to presume that it's compliant with regulations where you live.

If the issue with the listener is the plug then maybe you could build it into a decorative enclosure that includes a battery.

If the children's rooms are close together enough - maybe you could use 3 microphones (I am thinking of the low cost elements, nothing fancy) and take their inputs to a mixer, possibly including a preamplifier - then into the 'baby listener' in place of it's own microphone. While you would not be able to determine which room it at least alerts you to some activity. This same idea could be applied to a compliant low power FM transmitter (they are allowed here in US but with limitations). The straight line distance between the transmitter and reciever might not be far at all.

I realize that I haven't addressed whether or not you listen constantly or if the device needs to be triggered by sounds that are loud enough. In my own case I'd prefer to constantly listen rather than trust that I've got the level adjusted properly.

Locate the equipment in a closet or other inaccessible location. By the way, the mixer I refer to is relatively simple and made up of a handful of resistors and variable resistors.

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stevez

Someone Electro

Simpely build 3 FM bugs (Is a nother word for:low power radio transmiters) and tune tham to the same freq then have an FM radio to recive it.

You cod also take a part tha baby listener and stink it in to a small box whith baterys.And hiding it an an high place.It cod also be run by solar panels but there expensive

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zachtheterrible

How about taking the baby monitor that plugs into the wall, take it apart to make it smaller, and put it in a big nightlight?

My little sister had this night light that was supposed to look like a tea kettle(in other words, it was plenty big for a baby monitor). All u'd have to do is take the cord and split it between the light and the monitor.

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hotwaterwizard

How about an Amplifier in your office.
Then just wire a mic to each room.
You won't need to plug anything in inside any other room. Just run wires to each room and a microphone.
You can have all of them on at once or one at a time.

Attached Images

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